In a PWR (pressurized water reactor), light water is used as a nuclear reactor coolant and a neutron moderator, and used as high-temperature high-pressure water that is not boiled over a reactor internal. This high-temperature high-pressure water is transmitted to a steam generator to generate steam by heat exchange, and this steam is transmitted to a turbine generator to generate power. The pressurized water reactor transfers heat of high-temperature high-pressure primary cooling water to secondary cooling water by the steam generator, and generates water vapor by the secondary cooling water. In the steam generator, the primary cooling water flows into a large number of small heat-transfer tubes, and heat is transferred to the secondary cooling water flowing on the outside of the heat-transfer tubes, whereby water vapor is generated. The turbine is driven by the water vapor to generate power.
In the steam generator, a tube bundle shroud is arranged in a sealed hollow body so as to have a predetermined space between an inner wall surface of the body and the tube bundle shroud. Plural heat-transfer tubes, each having a reversed U-shape, are arranged in the tube bundle shroud. An end of each heat-transfer tube is supported by a tube sheet, and on a lower end of the body, an inlet channel head and an outlet channel head of the primary cooling water are formed. An inlet part of the secondary cooling water is formed above the tube bundle shroud in the body, and a steam-water separator and a moisture separator are arranged side by side in the vertical direction. A steam outlet is formed above these separators.
Therefore, the primary cooling water is fed to the plural heat-transfer tubes from a cooling water pipe via the inlet channel head, while the secondary cooling water is fed into the body from the inlet part. Heat exchange is done between the primary cooling water (hot water) flowing through the plural heat-transfer tubes and the secondary cooling water (cool water) circulating in the body. Accordingly the secondary cooling water absorbs heat to generate water vapor. Water is removed from the generated steam by the steam-water separator, and moisture is removed by the moister separator. The resultant steam is discharged from a steam outlet, while the primary cooling water that finishes the heat exchange is discharged from the outlet channel head.
In the steam generator thus configured, a large number of heat-transfer tubes provided in the body are supported by plural tube support plates and the tube sheet. The heat-transfer tubes and the tube sheet are inserted into a large number of holes formed on the tube support plates and the tube sheet, whereby the large number of heat-transfer tubes are supported by the tube support plates and the tube sheet without being vibrated. In this case, the tube support plates and the tube sheet have a large number of holes, so that these holes have to be formed by efficient drilling process.